Indoor air quality — what affects it and how to improve it
This article is for educational purposes only and is not a substitute for professional advice. Local codes, regulations, and best practices vary by region.
You spend most of your time indoors. The air you breathe affects your health. Poor indoor air quality causes respiratory problems, allergies, and discomfort. Indoor air problems include dust, allergens, mold spores, chemical off-gassing, combustion byproducts, and volatile organic compounds.
Most of these are addressable through ventilation, filtration, and moisture control. Understanding what affects air quality helps you improve it.
What Affects Indoor Air Quality
Dust and dust mites accumulate in homes, especially in carpets and upholstered furniture. People with allergies are sensitive to dust mites and their droppings.
Mold spores exist in air and grow when moisture is present. High mold spore counts indicate moisture problems.
Pollen enters through open windows and on clothing. Seasonal pollen counts affect people with allergies.
Pet dander from dogs and cats triggers allergies.
Chemical off-gassing from new furniture, carpets, and building materials. New materials release volatile organic compounds (VOCs) as they cure.
Combustion byproducts from gas appliances, fireplaces, and cars in garages. Carbon monoxide and nitrogen dioxide are concerns.
Cleaning products and air fresheners add chemicals to indoor air.
Humidity levels affect mold growth and dust mite populations. Very dry air causes respiratory irritation. Very humid air encourages mold.
Improving Ventilation
Fresh air exchange removes stale air and pollutants. Open windows on pleasant days. Operate bathroom and kitchen fans during and after use.
Mechanical ventilation (whole-house ventilation systems) continuously brings in fresh air while exhausting indoor air. These are especially helpful in tight, well-insulated homes that don’t have natural air leakage.
Proper exhaust fan operation vents moisture and odors outside, not into the attic or interior spaces.
Filtration
HVAC filters trap dust and large particles. Higher-MERV-rated filters (14+) trap more fine particles than basic filters. Change filters every 3 months or as needed.
Air purifiers with HEPA filters remove fine particles. These are useful for people with allergies or asthma.
Activated charcoal filters remove odors and some chemical compounds.
Portable purifiers help in specific rooms. Whole-house filters integrated with HVAC systems help throughout the home.
Moisture Control
Humidity between 30-50% is ideal. Below 30% causes dry air irritation. Above 50% encourages mold and dust mites.
Dehumidifiers lower humidity in damp basements or humid climates.
Bathroom and kitchen fans ventilate moisture outside.
Air conditioning cools and dehumidifies.
In dry climates or winter heating, humidifiers add moisture to prevent dry-air irritation.
Source Reduction
Open windows after bringing new furniture home to let off-gassing occur with fresh air exchange.
Use low-VOC paints, adhesives, and sealants in renovations.
Choose natural cleaning products when possible. Many standard cleaning products release chemicals.
Don’t use air fresheners. They mask odors without improving air quality. Ventilation is better.
Remove carpets in bedrooms (where you spend most of your respiratory time). Hard floors are easier to clean and don’t harbor dust mites.
Testing and Professional Help
Air quality testing is available through specialized labs. Cost is $300 to $1000+. This is useful if you suspect serious air quality problems but isn’t necessary for routine improvement.
An HVAC specialist can assess ventilation and suggest improvements.
An allergist can identify specific allergens affecting you.
Simple Improvements
Regular cleaning (vacuuming with HEPA filter, dusting with damp cloths) removes dust and allergens.
Changing HVAC filters more frequently (every 3 months) helps.
Opening windows on nice days brings fresh air.
Operating bathroom and kitchen fans removes moisture.
Controlling humidity (dehumidifiers, air conditioning) prevents mold growth.
Removing excess clutter reduces dust accumulation areas.
Washing bedding weekly in hot water kills dust mites.
Perspective
Perfect air quality in homes is unlikely. The goal is reducing major pollutants and allergens. For most people, basic ventilation, filtration, and moisture control are sufficient.
People with allergies or asthma might benefit from more aggressive air quality management (HEPA filters, humidifiers, allergen reduction).
Most improvements are inexpensive or free (opening windows, changing filters, operating fans). More expensive interventions (whole-house ventilation systems, professional air testing) are useful if basic measures don’t resolve problems.
© The Whole Home Guide